The iPod shuffle doesn't have a repeat setting. It only has a "shuffle mode" and "play in order".
In shuffle mode it will 'randomly' select the next song from it's library, playing in order will simply go from top to bottom.
In both cases it will repeat from the top once it has gone through all songs.

If your shuffle is repeating a single song or not all of the songs stored you may have set it to a playlist containing less or only a single song.